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7/15/2012 8:14 pm  #1


MN12 8.8 interchange question

I currently have a MN12 under my '70 F100 with an 8.8 center section. Can I simply grab a complete trac loc from a solid axle 8.8 & swap it into my housing? The Explorers came with 3.73 gears & trac loc. It would be a nice upgrade if it be that simple.

 

7/16/2012 9:32 am  #2


Re: MN12 8.8 interchange question

I would think so but a quick google search on MN12 (http://www.google.com/search?q=MN12&ie=utf-8&oe=utf-8&aq=t&rls=org.mozilla:en-US:official&client=firefox-a&channel=rcs) returned a variety of sites such as:
www.mn12.org/
www.midwestthundercats.com/
www.mamn12.com/

which on the surface look like look good resources.
Good luck!

 

7/16/2012 10:04 am  #3


Re: MN12 8.8 interchange question

Thanks for the info. I tried Google but did 8.8. Never thought about doing MN12 DUH

     Thread Starter
 

7/21/2012 4:19 pm  #4


Re: MN12 8.8 interchange question

elgemcdlf wrote:

I currently have a MN12 under my '70 F100 with an 8.8 center section. Can I simply grab a complete trac loc from a solid axle 8.8 & swap it into my housing? The Explorers came with 3.73 gears & trac loc. It would be a nice upgrade if it be that simple.

Yes and no.

The spider gears for the IRS trac-loc has a relief machined into it for the circlip.

http://forums.tccoa.com/showthread.php?t=108693

http://www.tccoa.com/articles/mn12-techinfo/traction-lok/traction-lok.htm

Options are to run with no clip
(supposedly done by a few people with no issues)

or

Machine in the step, this is the route I am going with once I get a few other projects done on my lathe.

I have seen a drawing with the correct numbers, but no difficult to measure a gear if you have one in front of you.

 

7/21/2012 6:40 pm  #5


Re: MN12 8.8 interchange question

Ok now for the silly question of the day. Why not just swap in the spiders from the IRS into the trac loc?

     Thread Starter
 

7/21/2012 9:13 pm  #6


Re: MN12 8.8 interchange question

elgemcdlf wrote:

Ok now for the silly question of the day. Why not just swap in the spiders from the IRS into the trac loc?

Besides the wear characteristics (you don't want to swap gears that have run with other gears) the design is different.

If you look at the picture of the gears, they have splines on the backside of them to drive the plates for the clutch pack.

Non-lsd gears have no provisions to mate with the clutch packs.

http://www.tccoa.com/articles/mn12-techinfo/traction-lok/traction-lok.htm

 

7/22/2012 8:05 am  #7


Re: MN12 8.8 interchange question

As I was moving the last of the posts from the original IRS forum I found a thread looking at exactly what this thread is talking about.  I think all the info on the thread I am reposting has ben covered in this thread but just in case I missed something I am reposting the link.
http://irsforum.boardhost.com/viewtopic.php?id=378


If it isn't broken..... modify it anyway!!!!
 

10/16/2012 9:26 pm  #8


Re: MN12 8.8 interchange question

Saw the post from Mike94531. If you swapped the spider and pinion gears from an mn12 trac lock diff, why would the wear characteristics matter. Those gears have already established a wear pattern with each other. Since the gears came from a trac lock diff, they would have the "splines" for the clutch pack. I am chiming in because I am interested in doing the same swap. Explorer diffs are a dime a dozen in the yards and would make a cheap and easy upgrade. Not trying to argue the point, just get a litle more input.

 

10/17/2012 4:42 am  #9


Re: MN12 8.8 interchange question

I am not positive but I think Mike was referring to a mismatched set of gears. Example 3.08 pinion with a 4.10 ring. The problem with an Explorer is 31 spline & the IRS is 28 spline. Explorers are a great place to get the ring & pinion though. You will need to take the spyders to a machine shop & have them grind a recess in the gear to match the IRS spyders as they are different but solid spyders can be adapted. You will want to find a carrier out of a police car or Ranger. You can swap out to 31 spline inner CV joints. I chose not to since you are still using 28 on the outside.

I ended up with a Limited Slip unit with 3.55 gears from a Mustang. Had a local machine shop put the groove in the spyders & have to date been very happy with no problems. I did originally buy a  unit from an Explorer (I knew it was 31 spline) with 4.10 gears for something like $50 at a local yard. I then posted it on Craigslist looking to trade for a 28 spline unit with 3.55gears. I got a hit within a couple days from a guy looking to move up to 31 spline axles in his Mustang. We swapped straight across. Naturally you would be best served if you found the 28 spline unit to start with which I did but had forgot about it when I went back to pull a unit.

Last edited by elgemcdlf (10/17/2012 4:45 am)

     Thread Starter
 

10/17/2012 8:19 am  #10


Re: MN12 8.8 interchange question

Thanks for the reply elgemcdlf. I understand that the Explorer diff is a 31 spline and the T-bird  is a 28 spline. I guess my question is if there is a physical difference in the side gears. I have the side and pinion gears out of a T-bird trac lock. Can I swap the side and pinion gears out of the Explorer and install the mn12 trac lock side and pinion gears, or is there a physical difference in those gears, meaning, the mn12 gears won't physically fit in the Explorer diff.

 

10/17/2012 5:26 pm  #11


Re: MN12 8.8 interchange question

They will fit just fine. It is all the same as long as your working with a pair of 8.8 rears & not the smaller MN12 carrier. I would match the ring with pinion unless the same ratio but even then I think I would just because.

     Thread Starter
 

10/17/2012 5:54 pm  #12


Re: MN12 8.8 interchange question

Thanks for the input elgemcdlf. Think I'll head to the yard this weekend and see what they have.

 

2/07/2013 5:20 pm  #13


Re: MN12 8.8 interchange question

I realize this is an old post but I an new to this forum. A better solution is to get the entire locker unit from a T-bird SC. A large proportion of them have the Trac-lok. While you are at it get the gear set. They are 3.26 as opposed to the lower number gears in the MN12.

 

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